It has long been a practice to dispose of waste material by burning it in an incinerator. In many incinerators, there is a main combustion chamber, and it is common to use forced air to sustain combustion in the main chamber. Generally, the heat of combustion from the waste material is sufficient to sustain combustion, but in the event the incoming waste does not have enough combustible material or is too wet, it is common to add fuel, such as coke or wood chips.
Incinerators have long been noted for their offensive smoke and airborne ashes. Accordingly, many modern incinerators employ a second combustion chamber to complete the combustion. However, where the waste being burned in the main combustion chamber is not entirely burned, resulting smoke is sometimes a fuel gas. When the fuel gas mixes with additional air in the second chamber, there is the potential for an explosion if the pilot light is not on or if the temperature during start up is not high enough.
Another problem with prior art incinerators is that with the flow of gaseous exhaust proceeding upwardly in the incinerator, there is a tendency for small particulate material, whether completely burned or not, to be carried through both the first and second combustion chambers and be discharged to the atmosphere. This becomes troublesome particularly when the waste material being burned is contaminated, such as by radio-activity or some other source of contamination. Where full and forced air are used to sustain combustion, this problem is intensified since the additional inflow of air would tend to increase the velocity of gaseous flow through the combustion chambers and thus have a greater tendency to carry particulate matter out as exhaust.
Contaminated waste material can take a great variety of forms. Some of this material, such as various organic material, is combustible, while other material, such as metal oxides, is non-combustible. With regard to radioactive waste, the combustible material can be incorporated in more common objects such as clothing, cardboard or wood containers, rags, etc., or material such as the ion-exchange resin used in nuclear power plants. There are a wide variety of such resins, and these are used to purify the water which is used in nuclear power plants. During this action of purification, the resin picks up highly radioactive materials, such as cesium, chromium, iron and the like. These resins may also have picked up fission products from the nuclear reactions. While the ion-exchange resins are essentially organic in nature, the exact compositions are quite often proprietary and thus not publicly known. However these are generally combustible to a considerable degree, but may contain some non-combustible material, such as metal oxide.
Also, waste material may come in either solid or liquid form, with the liquid form being either organic or aqueous. An example of an organic liquid which may be waste material is toluene. Quite often when toluene is burned in an incinerator, it produces a black smoke, and it is necessary to burn the black carbon smoke particles in a secondary combustion chamber. Another form of liquid waste material is that class of materials known as polycholorinated biphenyls, hereinafter referred to as "PCB's". Included in this class of materials are many organic chemicals of a toxic nature, such as dioxin, which is exceedingly toxic and resists decomposition by thermal means up to a temperature of perhaps as high as 1470.degree. F.
With regard to aqueous waste solutions, an example of these would be boric acid or sodium hydroxide. Also, such aqueous solutions could contain radioactive metal oxides.
In view of the foregoing, it is an object of my invention to provide a method and apparatus for converting waste material, and particularly hazardous waste material, to a relatively harmless condition.
It is a further object of my invention to provide such a method and apparatus that will handle a variety of combustible waste materials with substantially complete combustion by use of one combustion chamber.
It is yet another object to accomplish the above objects in a manner that substantially all or a relatively high proportion of the ash and dust residue resulting from combustion is captured and retained in a relatively harmless form.
These and other objects will become apparent from the following description.